1. Field of the Invention
The present invention relates to a disk array system, a host interface unit, a control method for a disk array system, and a computer program product for a disk array system. More particularly, the present invention relates to a disk array system which is capable of installing an additional host computer or a host computer and a disk, reducing an occurrence of a bottleneck path, unaffected by the configuration.
2. Description of the Related Art
A disk array system including multiple hard disk devices is widely used as a large-scale storage device for a computer. One example of the disk array system includes a disk array system that is upwardly scalable by additionally providing a hard disk device or the like.
JP2002-24085A discloses an example of the above-mentioned disk array system. The disk array system includes a host adapter, an array disk, a disk adapter, and a cache memory. The host adapter, the disk adapter, and the cache memory are connected to a common bus in a removable manner. The disk array system is configured to be upwardly scalable by additionally providing a host adapter or the like.
Next, another conventional disk array system is explained.
FIG. 9 is a block diagram showing a configuration of conventional large-scale disk array system 200. In FIG. 9, host interface card 202 activates, in response to a command from host computer 201, a data transfer between host computer 201 and cache memory 203. In a case of a cache miss when a read command is received, host interface card 202 issues a read command to disk interface card 204.
Disk interface card 204 transfers, in response to the instruction from host interface card 202, data from logical disk 205 to cache memory 203. Also, when cache memory 203 has write data, disk interface card 204 activates a data transfer from cache memory 203 to logical disk 205.
Also, another conventional disk array system is explained.
FIG. 10 is a block diagram showing a configuration of conventional storage subsystem 210 structured by combining small-size storage devices 213. In FIG. 10, multiple small-size storage devices 213 are connected to multiple host computers 211 through switch 212, to thereby construct a storage area network. Small-size storage device 213 activates, in response to a command from host computer 211, a data transfer between host computer 211 and cache memory 213, and also activates a data transfer between cache memory 214 and logical disk 215 as needed.